Preparation and performance of abradable environmental barrier coating on ceramic matrix composites

Abstract

With the application of shrouds made of silicon carbide ceramic matrix composite（SiC-CMCs），the abradable coating technology suitable for SiC-CMCs is urgently needed. The four-layer structure of BSAS（Ba0.75Sr0.25Al2Si2O8）-polyester-based abradable environmental barrier coating （A/EBCs） was prepared by atmospheric plasma spraying. The influence of process parameters on the porosity and the structural evolution of the layer at 1300 ℃ were investigated. The phase structure，microstructure and coating composition were characterized by XRD，SEM，EDS and TEM respectively. The results show that the porosity of BSAS-polyester abradable top layer is 26.4%-36.8%. And the temperature-sensitive parameters of BSAS-polyester particles are primary gas （argon） flow，second gas （hydrogen） flow and spraying distance. In contrast，the speed-sensitive parameters are primary gas （argon） flow. The primary gas （argon） flow has the opposite effect on the particle temperature and velocity of the BSAS-polyester. The abradable surface layer is oxidized at 1300 ℃ for 300 h and maintains monoclinic phase structure，stable stucture and composition，and locally precipitates spherical amorphous silicon oxide particles. Furthermore，the coating abradability was evaluated by high-temperature and high-speed scraping test. Nano-scale Ni-based superalloy particles adhesion on the surface of the coating are found，and the blade incursion depth ratio （IDR） is 20%，which meets the requirements of the abradable sealing coating.

Keywords

• abradable environmental barrier coating(a/ebcs)
• plasma spraying
• silicon carbide ceramic matrix composites(sic-cmcs)
• bsas
• high temperature performance